Filament electrode and fluorescent lamp

ABSTRACT

The disclosed subject matter includes a filament electrode that can include a filament coil connected with a pair of lead wires with confidence. It is possible for a fluorescent lamp using the filament electrode to emit light with a wider range while located in a thin tube. The filament electrode can include a pair of connecting pipes, a pair of lead wires located parallel to each other, and a filament coil including two connecting parts. Each of the two connecting parts of the filament coil can attach to respective ends of the pair of lead wires via the pair of connecting pipes via pressure bonding so as not to contact the connecting parts of the filament coil with the ends of the pair of lead wires located in the pair of connecting pipes and so as to align the structures. Thus, the filament electrode can be used even in a thin glass or quartz tube and can provide an effective heat-shield operation.

This application claims the priority benefit under 35 U.S.C. §119 ofJapanese Patent Application No. 2006-353194 filed on Dec. 27, 2006,which is hereby incorporated in its entirety by reference.

BACKGROUND

1. Field

The presently disclosed subject matter relates to a filament electrodeand to a fluorescent lamp using the same. More particularly, thedisclosed subject matter relates to a filament electrode that canconnect a filament coil with a pair of lead wires with confidence andcan be employed even if an inner diameter of the light source is thin.The disclosed subject matter also relates to a fluorescent lamp usingthe above connection structures that can decrease both end areas whichdo not emit light and can allow emission with a wider range.

2. Description of the Related Art

A conventional hot-cathode fluorescent lamp (HCFL), cold-cathodefluorescent lamp (CCFL) and the like can include respective electrodesfor supplying a power supply at both ends of a light tube that caninclude a glass tube, silica tube, quartz tube, or other type ofarc/luminescence tube. The conventional filament electrode is composedof, for example, a filament coil that is connected to a pair of leadwires. The respective filament coils can be encapsulated in the lighttube that includes a filler gas. Respective pairs of lead wires canextend from the light tube to an area outside of the light tube alongand can be sealed within the tube structure in an air proof state.Therefore, when supplying the respective filament coils with a powersupply via the respective pairs of lead wires, the conventional HCFL,CCFL and the like emit by generating a discharge in the light tube.

FIGS. 8A&B show a conventional structure of the above-described filamentelectrode, wherein FIG. 8(A) shows a state before fixing the lead wires2 a and 2 b to a filament coil 3 via pressure bonding and FIG. 8(B)shows a state after fixing via pressure bonding. The filament electrode1 is composed of both the filament coil 3 and the pair of lead wires 2a, 2 b, which are made from respectively different materials. Therefore,the filament coil 3 and the pair of lead wires 2 a, 2 b should be fixedto each other. Each of the pair of lead wires 2 a, 2 b can be composedof a conductive metallic material and located parallel or substantiallyparallel to each other. The filament coil 3 is composed of, forinstance, a tungsten, a doped tungsten and the like and includes a coilbody 3 a formed in a spiral and two connecting parts 3 b, 3 c jutted outfrom both ends of the coil body 3 a in a straight line.

The filament coil 3 is attached to the pair of lead wires 2 a, 2 b asshown in FIGS. 8(A) and (B). That is to say, the filament coil 3includes: each of the two connecting parts 3 b, 3 c thereof contactingeach end of the pair of lead wires 2 a, 2 b perpendicular to each other;each end of the pair of lead wires 2 a, 2 b bending in a direction asshown by the arrows in FIG. 8A; each end of the pair of lead wires 2 a,2 b sandwiching each of the two connecting parts 3 b, 3 c therebetween;and each end of the pair of lead wires 2 a, 2 b crimping each of the twoconnecting parts 3 b, 3 c therebetween. Thus, the filament coil 3 isattached to the pair of lead wires 2 a, 2 b by fixing the two connectingparts 3 b, 3 c thereof to each end of the pair of lead wires 2 a, 2 bwith pressure bonding.

However, according to the conventional filament electrode 1 shown inFIGS. 8A&B, because the filament coil 3 extends in a direction towardsan inner diameter of the light tube when manufacturing a HCFL and thelike, it is difficult for a thin inner diameter type HCFL light tube andthe like to employ the filament electrode 1.

Therefore, an electrode structure as shown in FIG. 9 is also well-known.The filament electrode 4 includes a pair of lead wires 2 a, 2 b locatedparallel to each other and attached to a filament coil 5 that is longerin a direction extending with the length of the pair of lead wires 2 a,2 b (downwards in FIG. 9) than its interval. The above filament coil 5is composed of a coil body 5 a forming double helical so as to wrap inboth directions of left and right around a central axis thereof and twoconnecting parts 5 b, 5 c extending symmetrically from both ends of thecoil body 5 a in parallel to the central axis, respectively.

The filament coil 5 includes: each of the two connecting parts 5 b, 5 cthereof contacting each end of the pair of lead wires 2 a, 2 b in linewith each other; each of the two connecting parts 5 b, 5 c thereof beingwelded with each end of the pair of lead wires 2 a, 2 b using a spotwelding, a laser welding and the like. Therefore, each of the twoconnecting parts 5 b, 5 c are fixed to each end of the pair of leadwires 2 a, 2 b. Thus, the filament coil 5 is attached to the pair oflead wires 2 a, 2 b by welding each of the two connecting parts 5 b, 5 cthereof with each end of the pair of lead wires 2 a, 2 b. In the abovedescribed electrode structure, heat generated from the filament coil 5during light-emission is directly transmitted to the pair of lead wires2 a, 2 b and is radiated.

A revised example of the above described filament electrode 4 isdisclosed in, for example, Patent Document No. 1 (Japanese PatentApplication Laid Open No. JP2005-235749). FIG. 10 is the disclosedelectrode structure in accordance with Patent Document No. 1. Each oftwo connecting parts 5 a, 5 b of a filament coil 5 is weld to each of apair of heat-tabs 6 a, 6 b and each end of a pair of lead wires 2 a, 2 bis also welded to each of the pair of heat-tabs 6 a, 6 b. That is tosay, the filament coil 5 is attached to the pair of lead wires 2 a, 2 bvia the pair of heat-tabs 6 a, 6 b with a weld. Therefore, the aboveelectrode structure of FIG. 10 is configured to radiate heat generatedfrom the filament coil 5 to the pair of lead wires 2 a, 2 b via the pairof heat-tabs 6 a, 6 b.

FIG. 11 shows an electrode structure used for a bulb having doublefilaments. According to the electrode structure of the bulb 7 shown inFIG. 11, each of two filament coils 7 a is welded to each of two leadwires 7 b via each of two pipes 7 c. Therefore, the electrode structureof the bulb 7 is configured to radiate heat generated from each of thetwo filament coils 7 a to each of two lead wires 7 b via each of the twopipes 7 c.

An exemplary electrode structure of a fluorescent lamp is disclosed inPatent Document No. 2 (Japanese Patent Application Laid Open No.Hei04-245161). FIG. 12 is the disclosed electrode structure of thefluorescent lamp in accordance with Patent Document No. 2. Thefluorescent lamp 8 includes: a mixture 8 c disposed in a metallic pipe 8b, the mixture 8 c including a mixture of metallic powder with anemitter powder; the mixture 8 c is pressed during manufacture so as toform a hole around a central axis thereof; the metallic pipe 8 b issintered to an electrode 8 a located therein along with the mixture 8 c;the metallic pipe 8 b can then be tightened up at a back end thereoftowards a central axis of lead wire 8 e that passes through a endportion of glass tube 8 d; thereby fixing the electrode 8 a to the leadwire 8 e.

An exemplary electrode structure of a halogen bulb is disclosed inPatent Document No. 3 (Japanese Patent Application Laid Open No.Hei11-297272). FIG. 13 is the disclosed electrode structure of thehalogen bulb 9. According to Patent Document No. 3, an electrode 9 a isfixed to a lead wire 9 b via a pipe 9 c with a weld or a pressurebonding. In this case, because the pipe 9 c is configured with amaterial of which the coefficient of thermal expansion (CTE) is biggerthan that of tungsten which is the material of the electrode 9 a, thepipe 9 c expands because of heat generated from the electrode 9 a duringlight-emission of the halogen bulb 9 and a gap is caused between theelectrode 9 a and the lead wire 9 b. Thus, the heat generated from theelectrode 9 a cannot be directly transmitted to the lead wire 9 b and anoxidation of the electrode 9 a can be prevented.

The above-referenced Patent Documents are listed below and areincorporated herein by reference.

1. Patent Document No. 1: Japanese Patent Application Laid OpenJP2005-235749

2. Patent Document No. 2: Japanese Patent Application Laid OpenHei04-245161

3. Patent Document No. 3: Japanese Patent Application Laid OpenHei11-297272

However, in the electrode structure of the filament electrode 4 shown inFIG. 9, the filament coil 5 is fixed to the pair of lead wires 2 a, 2 bby welding each of the two connecting parts 5 b, 5 c thereof with eachend of the pair of lead wires 2 a, 2 b. Therefore, when welding each ofthe two connecting parts 5 b, 5 c with each end of the pair of leadwires 2 a, 2 b, a recrystallization of tungsten of the filament coil 5can be caused, especially in the welding area. Therefore, the strengthof fixing therebetween may become weak. As the result, the filament coilmay become detached from the pair of lead wires 2 a, 2 b when a shock isapplied thereto. A decrease of the fixing strength/intensity in a weldsimilar to the above-described weld can also be realized in theelectrode structure of FIG. 10 and the bulb 7 of FIG. 11 describedabove.

In the above-described electrode structures of FIG. 8 to FIG. 10, heatgenerated from the filament coils 3, 5 is transmitted to the pair oflead wires 2 a, 2 b and is transmitted to a sealing portion between thepair of lead wires 2 a, 2 b and the glass tube. Thus, because a gap iscaused in the sealing portion between the pair of lead wires 2 a, 2 band the glass tube due to a difference between the CTE of glass of thesealing portion and that of a material of the pair of lead wires 2 a, 2b, a filler gas in the glass tube may leak out. On the other hand, whena distance from each of the two connecting parts 3 b, 3 c and 5 b, 5 cof the filament coils 3, 5 to the sealing portion is extended byextending a length of the pair of lead wires 2 a, 2 b, the end areas ofthe tube that are not designed to emit light expands. Such an electrodestructure is not desired for employment as a light source such as a backlight unit and the like, because the both end areas in which light isnot emitted is large.

In the fluorescent lamp 8 in accordance with Patent Document No. 2, theelectrode 8 a fixes the lead wire 8 e by being sintered with themetallic pipe 8 b and by fixing the back end of the metallic pipe 8 b tothe lead wire 8 e with a pressure bonding. However, because the sinterbonding process for fixing the electrode 8 a to the metallic pipe 8 b isrequired, the process for manufacturing becomes complex.

In the electrode structure of the halogen bulb 9 in accordance withPatent Document No. 3, because the pipe 9 c expands bigger than both theelectrode 9 a and the lead wire 9 b during light-emission of the halogenbulb 9, a gap appears between the electrode 9 a and the lead wire 9 b.Thus, heat generated from the electrode 9 a is not transmittedefficiently to the lead wire 9 b because of the gap between theelectrode 9 a and the lead wire 9 b, and the gap prevents the electrode9 a from oxidizing. However, because a transmission of the heat isshielded by the slight gap caused during light-emission of the halogenbulb 9 due to the difference of CTE between materials of both theelectrode 9 a and the lead wires 9 c and a material of the pipe 9 c, theheat-shield operation may be unstable or unpredictable, and electricalcontact between the electrode 9 a and the lead wire 9 b may also becomedefective.

The disclosed subject matter has been devised to consider the above andother problems and characteristics. Thus, embodiments of the disclosedsubject matter can include a filament electrode and associated stem thatdo not cause (or depreciates) some or all of the above-described variousproblems and can connect a filament coil with a pair of lead wires withconfidence and strength. In addition, the filament electrode can beemployed even if an inner diameter of a light source is very thin. Thedisclosed subject matter can also include a fluorescent lamp using thefilament electrode that is configured to decrease that portion of theend areas that do not emit light, and to emit light with a wide range.

SUMMARY

The presently disclosed subject matter has been devised in view of theabove and other problems and characteristics in the conventional art,and to make certain changes to the existing electrode structures. Anaspect of the disclosed subject matter includes providing a filamentelectrode and associated stem that can connect a filament coil with apair of lead wires with confidence and strength for supplying a powersupply absolutely and which prevents leaks in a sealing portion.Furthermore, the filament electrode can be used even in a thin innerdiameter tube.

Another aspect of the disclosed subject matter includes providing afluorescent lamp using the above described filament electrode that candecrease both end areas which are not configured for emission of lightand which can emit light with a wider range. Thus, because thefluorescent lamp can be formed to be thin and can extend alight-emission area thereof, it can be employed as a light source for aback light unit, etc.

According to an aspect of the disclosed subject matter, a filamentelectrode can include: a pair of connecting pipes formed in a tubularmanner; a pair of lead wires located parallel with respect to eachother, each with an end thereof attached to a respective end of the pairof connecting pipes in a telescoped state via pressure bonding, and eachwith an opposite respective end thereof exposed in order to supply apower supply; and a filament coil including two connecting parts, eachof the two connecting parts attached to each of the opposite respectiveends of the pair of connecting pipes in a telescoped state via pressurebonding so as not to contact the ends of the pair of lead wires in eachof the pair of connecting pipes.

In the above described exemplary filament electrode, the filamentelectrode can also include the pair of connecting pipes that arecomposed of a conductive material having a coefficient of thermalconductivity that is smaller than that of the pair of lead wires. Thepair of connecting pipes can also include a squeezing part between eachend thereof and each respective other end thereof. The squeezing partcan be formed in a tapered shape so as to shrink from each first endthereof towards each respective other end thereof. In addition, the pairof connecting pipes can also function as a getter, for example, by beingmade of certain reactive materials to ensure and maintain properatmospheric chemical make-up and pressure qualities within the tube.

In the above described exemplary filament electrode, the filamentelectrode can further include a glass bead formed in a circular manner,wherein the glass bead is provided around a proximal portion of eachexposed end of the pair of lead wires and can achieve an air proof statebetween the glass bead and the pair of lead wires. The above filamentelectrode including the glass bead can be a convenient structure formanufacturing a fluorescent lamp as described later.

According to the above described exemplary filament electrode, becauseeach of the two connecting parts of the filament coil can connect eachcorresponding end of the pair of lead wires via the pair of connectingpipes, a power supply can be provided to the filament coil with greatconsistency. In that case, because each of the two connecting parts ofthe filament coil can align each of the pair of lead wires via each ofthe pair of connecting pipes in line with a direction parallel orco-axial with a longitudinal axis or length of the tube, the filamentelectrode can be installed in the tube with confidence even if an innerdiameter of tube is thin.

In addition, because each of the two connecting parts of the filamentcoil can firmly attach to each of the pair of connecting pipes viapressure bonding, the fixing intensity does not weaken due torecrystallization of tungsten of the filament coil. Thus, the filamentcoil is not prone to detachment from the pair of lead wires and can beconfidently supplied with a power supply.

Furthermore, when the pair of connecting pipes is composed of a materialfor which the coefficient of thermal conductivity is smaller than thatof the pair of lead wires, because heat generated from the filament coilis then not transmitted efficiently to the pair of lead wires, a gapthat may otherwise be caused between the glass bead and the pair of leadwire can be prevented and therefore a filler gas in the glass tube canbe prevented from leaking out.

Another aspect of the disclosed subject matter includes a fluorescentlamp using the immediately above-described filament electrode that caninclude: a glass, quartz or other tube formed in a tubular fashion, aninner surface thereof forming a phosphor layer, and both ends thereofproviding respective filament electrodes so as to be located opposite toeach other and so as to be fixed between both ends of the tube and therespective glass beads provided at the respective pairs of lead wires intheir respective air proof state; and a filler gas can be located in thetube.

According to the above described exemplary fluorescent lamp, because thepair of lead wires is not heated to an extreme degree as describe above,the one end of the pair of lead wire can be located near the end of thetube. Thus, the fluorescent lamp can be configured to decrease theportions of the end areas at which light is not emitted and can beconfigured to emit a light with a wide area.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics and features of the disclosed subjectmatter will become clear from the following description with referenceto the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view showing an embodiment of anelectrode structure for a filament electrode made in accordance withprinciples of the disclosed subject matter;

FIG. 2 is a schematic perspective view showing a halfway state in anexemplary manufacturing process for the filament electrode shown in FIG.1;

FIG. 3 is an enlarged cross-section view showing a pair of connectingpipes of the filament electrode shown in FIG. 1;

FIG. 4 is a partial cross-section view depicting an installed state forthe filament electrode of FIG. 1 in a fluorescent lamp.

FIGS. 5(A) and (B) are enlarged cross-section views showing a secondexemplary embodiment of a pair of connecting pipes for a filamentelectrode made in accordance with principles of the disclosed subjectmatter;

FIG. 6 is a schematic perspective view showing a third exemplaryembodiment of an electrode structure for a filament electrode made inaccordance with principles of the disclosed subject matter;

FIGS. 7(A)-(C) are a schematic perspective view for a description ofmisalignment in a sideward direction of two connecting parts of afilament coil to a pair of connecting pipes in the filament electrodeshown in FIG. 1; a schematic perspective view depicting shapes offilament coils in a C-6 type bulb for a vehicular lamp; and a schematicperspective view depicting the shape of filament coils in a C-8 typebulb, respectively;

FIGS. 8(A)-(B) are schematic perspective views showing a conventionalelectrode structure, wherein FIG. 8(A) shows a state before pressurebonding and FIG. 8(B) shows a state after pressure bonding;

FIG. 9 is a schematic perspective view depicting a second example of aconventional electrode structure;

FIG. 10 is a schematic cross-section view depicting a third example of aconventional electrode structure;

FIG. 11 is a schematic cross-section view depicting a fourth example ofa conventional electrode structure;

FIG. 12 is a schematic cross-section view depicting a fifth example of aconventional electrode structure; and

FIG. 13 is a schematic cross-section view depicting a sixth example of aconventional electrode structure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the disclosed subject matter will now bedescribed in detail with reference to FIG. 1 to FIG. 7. FIG. 1 is aschematic perspective view showing an example of an electrode structurefor a filament electrode made in accordance with principles of thedisclosed subject matter. The filament electrode 10 can include a pairof lead wires 11, 12, a filament coil 13 and a pair of connecting pipes14, 15.

The pair of lead wires 11, 12 can be composed of a conductive metallicmaterial and can be located parallel with respect to each other. Thefilament coil 13 can be composed of, for instance, a tungsten (W), arhenium tungsten (W—Re), a doped tungsten and the like.

The above filament coil 13 can include a coil body 13 a formed in adouble helical and two connecting parts 13 b, 13 c extending from bothends of the coil body 13 a in a direction parallel with a central axisthereof (downwards in FIG. 1). The coil body 13 a can be formed, forexample, as a double helical so as to wrap in both left and rightdirections around the central axis thereof as shown in FIG. 1. However,a shape of coil body 13 a should not be limited to the shape of FIG. 1.The shape can be formed in a voluntary fashion, for example, C-6 or C-8like a vehicular bulb. In addition, the filament coil 13 can be coatedwith an emissive material, for instance, an oxide composed of a barium(Ba), a strontium (Sr), a calcium (Ca) and the like on a surfacethereof.

The above-described pair of connecting pipes 14, 15 can be composed of aconductive metallic material and can be formed in a hollow tubularconfiguration. The pair of connecting pipes 14, 15 can be composed of ametallic material for which the coefficient of thermal conductivity issmaller than that of the pair of lead wires 11, 12, such as a nickel andan iron metal, for which the coefficient of thermal conductivity is lessthan 115 W/m·K.

The pair of connecting pipes 14, 15 can be configured as and function asa getter. When the pair of connecting pipes 14, 15 is composed of amaterial having a getter function or is formed with a material having agetter function coated on an inner surface or an outer surface of thepair of connecting pipes 14, 15, the getter function can be activated inthe pair of connecting pipes 14, 15. The getter material can be coatedvia vapor deposition or other known coating or fixation method.

When the pair of connecting pipes 14, 15 includes a getter function, thepair of connecting pipes 14, 15 can be composed of, for example, amaterial of titanium series and a material of zirconium series. When asurface of the pair of connecting pipes 14, 15 is formed of acomparatively low conductive material having a getter function, thematerial can form an outer surface of the pair of pipes 14, 15.

A description of the specific electrode structure for the filamentelectrode 10 will now be given. Each first end 14 a, 15 a of the pair ofconnecting pipes 14, 15 can be telescoped onto an end of the pair oflead wires 11, 12 located therein as shown in FIG. 2. Each first end 14a, 15 a of the pair of connecting pipes 14, 15 can be constricted overeach end of the pair of lead wires 11, 12 from both sideward directionsas show in FIG. 3. Thus, the pair of lead wires 11, 12 can be attachedto the pair of connecting pipes 14, 15 so that each the ends of thewires 11, 12 are sandwiched in each distorted first end 14 a, 15 a ofthe pair of connecting pipes 14,15 and are thus fixed via pressurebonding. However, the pair of lead wires 11, 12 can also be attached tothe pair of connecting pipes 14, 15 by fixing each end of the wires 11,12 to each respective first end 14 a, 15 a of the pair of connectingpipes 14, 15 with a weld. Each of the other ends of the pair of leadwires 11, 12 can be exposed in order to provide a power supply to thelamp via a socket and the like.

Each opposite end 14 b, 15 b of the pair of connecting pipes 14, 15 canbe telescoped onto two connecting parts 13 b, 13 c of the filament coil13 as shown in FIG. 3. Each opposite end 14 b, 15 b of the pair ofconnecting pipes 14, 15 can be constricted over each end of the twoconnecting parts 13 b, 13 c of the filament coil 13 from sidewarddirections. Thus, the filament coil 13 can be attached to the pair ofconnecting pipes 14, 15 so that each end of two connecting parts 13 b,13 c is sandwiched in a respective distorted opposite end 14 b, 15 b ofthe pair of connecting pipes 14, 15 and is fixed via pressure bonding.

In the above-described two attachment configurations for the pair ofconnecting pipes 14, 15, pair of lead wires 11, 12, and two connectingparts 13 b, 13 c of the filament coil 13, either of the ends can be thefirst to be attached and/or both of the ends can be attached at the sametime. However, when each end of the pair of lead wires 11, 12 isattached to each first end 14 a, 15 a of the pair of connecting pipes14, 15 with a weld, for example, after fixing with the weld, thefilament coil 13 can be attached to the pair of connecting pipes 14, 15via pressure bonding. The reason why the weld is carried out firstbecause it can absolutely eliminate an effect of transmitting heat tothe filament coil 13 during the weld process.

The filament electrode 10 in accordance with an exemplary embodiment ofthe disclosed subject matter can be constituted as described above. Amanufacturing process for the filament electrode 10 can include:providing the pair of connecting pipes 14, 15 with each first end 14 a,15 a telescoped over respective ends of the pair of lead wires 11, 12;attaching each end of the pair of lead wires 11, 12 to respective firstends 14 a, 15 a of the pair of connecting pipes 14, 15 with a weld orvia pressure bonding; attaching each of the opposite ends 14 b, 15 b ofthe pair of connecting pipes 14, 15 by telescoping them over each end oftwo connecting parts 13 b, 13 c of the filament coil 13; and attachingeach end of the two connecting parts 13 b, 13 c of the filament coil 13to respective opposite ends 14 b, 15 b of the pair of connecting pipes14, 15 via pressure bonding.

In this case, each end of the two connecting parts 13 b, 13 c of thefilament coil 13 can be configured to telescope into respective oppositeends 14 b, 15 b of the pair of connecting pipes 14, 15 while also notcontacting respective ends of the pair of lead wires 11, 12 whichtelescope into respective first ends 14 a, 15 a of the pair ofconnecting pipes 14, 15. This is accomplished by allowing each end ofthe two connecting parts 13 b, 13 c of the filament coil 13 to telescopewithin the opposite ends 14 b, 15 b of the connecting pipes 14, 15 so asto maintain a predetermined interval between each end of the twoconnecting parts 13 b, 13 c and each end of the pair of lead wires 11,12 in each of the pair of connecting pipes 14, 15. Thus, the filamentcoil 13 and the pair of lead wires 11, 12 can be fixed with respect toeach other at a predetermined interval via the pair of connecting pipes14, 15 in the filament electrode 10.

In the above-described structure, because the filament coil 13 can beattached in each of the opposite ends 14 b, 15 b of the pair ofconnecting pipes 14, 15 via pressure bonding, recrystallization of amaterial such as tungsten and the like composing the filament coil 13cannot create a weld-like structure. Thus, because the fixing intensityin the filament electrode 10 does not become weak, the filament coil 13should not become detached from the ends of the pair of lead wires 11,12 and, therefore, reliability of the filament electrode 10 canincrease.

Furthermore, because each end of the two connecting parts 13 b, 13 c ofthe filament coil 13 can be attached to respective ends of the pair oflead wires 11, 12 via the pair of connecting pipes 14, 15, the filamentelectrode 10 can extend in a direction parallel with a longitudinal axisof the tube. Thus, even if a diameter of the tube is thin, the filamentelectrode 10 can be easily installed in the thin tube.

FIG. 4 is a partial cross-section view depicting a state in which thefilament electrode 10 is installed in one end of a fluorescent lamp, andin which the other end of the lamp can be symmetrical and include thesame filament electrode 10. Before manufacturing a fluorescent lamp andthe like, the filament electrode 10 can form a stem wherein a bead 18made of glass, quartz, or the like, is provided around a proximalportion of a pair of lead wires 11, 12 in a substantially or totally airproof state between the bead 18 and the pair of lead wire 11, 12. Theabove described filament electrode including the bead 18 can be aconvenient structure for manufacturing a fluorescent lamp. The bead 18can be provided at a bead location on the pair of lead wires 11, 12proximal with respect to the connection location at which the pair oflead wires 11, 12 are attached to the pair of connecting pipes 14, 15.The connection location can be located between the bead location and thefilament coil 13.

The fluorescent lamp 16 can include: a tube 17 configured in a tubularshape from glass, quartz, or the like, an inner surface of the tube 17can include a phosphor layer, and both ends 17 a of the tube 17 caninclude respective filament electrodes 10 so as to be located oppositeto each other and so as to be fixed between both ends 17 a of the glasstube 17 and the respective glass beads 18 provided on the respectivepairs of lead wires 11, 12 in their respective air proof states. Afiller gas can be located in the tube 17.

When a power supply is provided between respective ends of the pairs oflead wires 11, 12, the respective filament coils 13 can be heated andcan operate as respective heaters. Thus, because the fluorescent lampcan generate a discharge in the tube 17 with a discharge voltage betweeneach of the filament electrodes 10 attached to both ends 17 a of thetube 17, the fluorescent lamp 16 can emit light.

In this case, when the pair of connecting pipes 14, 15 is composed of amaterial having a smaller coefficient of thermal conductivity than thatof the pair of lead wires 11, 12, it is difficult to transmit heatgenerated from the filament coil 13 during light-emission of thefluorescent lamp 16 to the pair of lead wires 11, 12 via the pair ofconnecting pipes 14, 15. Thus, in the sealing portions of both ends 17 aof the tube 17 and the respective beads 18 (and between the respectivepairs of lead wires 11, 12 and the respective glass beads 18) the fillergas in the tube 17 can be prevented from leaking out due to a gap causedby differences of CTE between the ends 17 a of the tube 17 and therespective beads 18, and/or based on differences of CTE between therespective pairs of lead wires 11, 12 and the respective beads 18.

In addition, because the pair of lead wires 11, 12 are not extremelyheated, each end of the respective pairs of lead wires 11, 12 can belocated near respective ends 17 a of the tube 17. Thus, whenmanufacturing a fluorescent lamp using other conventional types offilament electrodes in a tube as long as the tube 17, theabove-described fluorescent lamp using the filament electrode 10 canemit brighter light than the other conventional fluorescent lamp.

Furthermore, because the filament coil 13 can be coated with an emissivematerial, the emissive material can emit an electron in the tube 17 byheating the filament coil 13 and the discharge in the tube 17 can beaccelerated. In addition, because the pair of connecting pipes 14, canbe configured to function as a getter, the pair of connecting pipes 14,15 can absorb gas molecules such as impure substances and the likelocated in the tube 17. Therefore, the fluorescent lamp 16 can improveits discharging state, its sputter and the like in the tube 17.

A second exemplary embodiment of the disclosed subject matter will nowbe given with reference to FIGS. 5(A)-(B). Relevant parts of thefilament electrode 20 of the second exemplary embodiment are shown inFIGS. 5(A)-(B), wherein the same or similar elements shown in FIGS. 1and 4 are referenced by same reference numerals. A difference betweenthe filament electrode 20 and the filament electrode 10 can include apair of squeezing parts 14 c, 15 c between each first end 14 a, 15 a andeach opposite end 14 b, 15 b of the pair of connecting pipes 14, 15. Thepair of squeezing parts 14 c, 15 c can be formed thinner than both thefirst ends 14 a, 15 a and the opposite ends 14 b, 15 b and can also spanthe first and opposite ends in an arch formed as shown in FIG. 5(B).

According to the second exemplary embodiment, when each of the twoconnecting parts 13 b, 13 c of the filament coil 13 telescopes into eachof the opposite ends 14 b, 15 b of the pair of connecting parts 14, 15,the pair of squeezing parts 14 c, 15 c can operate as stoppers of thetwo connecting parts 13 b, 13 c of the filament coil 13. In addition,when each end of the pair of lead wires 11, 12 telescopes into eachfirst end 14 a, 15 a of the pair of connecting parts 14, 15, the pair ofsqueezing parts 14 c, 15 c can operate as stoppers of the lead wires 11.12 with respect to the pair of connecting parts 14, 15. Thus, contactbetween each of the two connecting parts 13 b, 13 c of the filament coil13 with each end of the pair of lead wires 11, 12 located in the pair ofconnecting parts 14, 15 can be avoided without exception.

In addition, because it can become harder for heat generated from thefilament coil 13 during light-emission of the fluorescent lamp 16 to betransmitted via connecting pipes 14, 15 to the pair of lead wires 11,12, each of the ends of the pair of lead wires 11, 12 can be locatednearer respective ends 17 a of the tube 17. Thus, those end areas inwhich light is not emitted in the tube 17 can be made smaller and thefluorescent lamp can thus emit light with a wider range.

A third exemplary embodiment of the disclosed subject matter will now bedescribed with reference to FIG. 6. FIG. 6 shows a filament electrode 30that can be configured similar to the filament electrode 10 shown inFIG. 1. Thus, the same or similar elements in FIG. 6 are referencedusing the same reference numerals as those in FIG. 1. A differencebetween the filament electrode 30 and the filament electrode 10 caninclude providing a pair of connecting pipes 31, 32 in place of the pairof connecting pipes 14, 15 which are shown as formed in a generallycylindrical tubular shape. The pair of connecting pipes 31, 32 canformed such that they are tubular while also shrinking in diameter alongtheir longitudinal axis in a tapered manner and shape from each firstend 31 a, 32 a towards each opposite end 31 b, 32 b of the pair ofconnecting pipes 31, 32.

According to the third exemplary embodiment, when the diameter of eachof the apertures of the opposite ends 31 b, 32 b corresponds with arespective diameter of the two connecting parts 13 b, 13 c of thefilament coil 13, the filament coil 13 can be exactly attached to thepair of lead wires 11, 12 so that each of the two connecting parts 13 b,13 c thereof aligns with each of the pair of connecting pipes 31, 32.Therefore, a problem in that each of the two connecting parts 13 b, 13 cof the filament coil 13 is misaligned with each of the pair ofconnecting pipes 14, 15 by an amount “d” as shown in FIG. 7(A) cannot bepresent in the above-described exemplary embodiment. Thus, the filamentcoil 13 can be attached to the pair of lead wires 11, 12 with a highpositioning accuracy.

Thus, the disclosed subject matter can provide a filament electrode thatcan connect a filament coil with a pair of lead wires with confidenceand strength and with minimal or no leakage at the sealing portions,which can be the result and benefits of an effective heat-shieldoperation. The filament electrode can also be employed in a thin innerdiameter tube. Furthermore, the disclosed subject matter can provide afluorescent lamp using a filament electrode that can decrease both endareas in which light is not typically able to be emitted such that lightcan be emitted with a wider range.

In the above-described exemplary embodiments, the pair of connectingpipes 14, 15 can include materials or be configured of materials thatprovide a getter function. However, it is possible to provide separateor other structures that function as a getter. In addition, theconnecting pipes 14, 15 are shown as cylindrical with a circularcross-section. However, this shape can be varies greatly and remainwithin the spirit and scope of the disclosed subject matter. Forexample, the pipes 14, 15 can be configured to have a polygonalcross-section, non-symmetrical cross-section, oval cross-section orother cross section. In addition, the shape of the pipes 14, 15 canchange along the longitudinal axis of the pipes 14, 15. In particular,the wall thickness and shape can vary at different locations along thepipes 14, 15 to facilitate pressure bonding and the like. The filamentcoil 13 can be formed in a double helical shape. However, it iscontemplated that the shape of the filament coil 13 can be formed invarious other shapes and configurations without limitation. In addition,the electrodes 10, 20 and 30 of the exemplary embodiment can beconfigured for use in a fluorescent lamp. However, these electrodes canalso be configured for use in other types of bulbs and the like withoutdeparting from the spirit and scope of the presently disclosed subjectmatter.

While there has been described what are at present considered to beexemplary embodiments of the invention, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover such modifications as fall within the true spiritand scope of the invention. All conventional art references describedabove are herein incorporated in their entirety by reference.

1. A filament electrode comprising: a pair of connecting pipesconfigured in a tubular shape, each of the connecting pipes including afirst end and an opposite end; a pair of lead wires locatedsubstantially parallel with respect to each other, each of the leadwires having a first end attached to a respective first end of the pairof connecting pipes in a telescoped state via pressure bonding, and eachof the lead wires having an opposite end exposed in order to receive apower supply; and a filament coil including two connecting parts, eachof the two connecting parts including a connecting end attached to arespective opposite end of the pair of connecting pipes in a telescopedstate via pressure bonding such that each respective connecting end ofthe connecting part is spaced from and does not contact a respectivefirst end of the pair of lead wires.
 2. The filament electrode accordingto claim 1, wherein the pair of connecting pipes is composed of aconductive material having a coefficient of thermal conductivity smallerthan a coefficient of thermal conductivity of the pair of lead wires. 3.The filament electrode according to claim 2, wherein the pair ofconnecting pipes includes a squeezing part located between each firstend of the pair of connecting pipes and each respective opposite end ofthe pair of connecting pipes.
 4. The filament electrode according toclaim 3, wherein the pair of connecting pipes includes a getter materialthat functions as a getter.
 5. The filament electrode according to claim4, further comprising: a bead formed in a substantially circular shape,wherein the bead is located adjacent the opposite exposed end of atleast one of the pair of lead wires in an air proof state between thebead and the at least one of the pair of lead wires.
 6. The filamentelectrode according to claim 3, further comprising: a bead formed in asubstantially circular shape, wherein the bead is located adjacent theopposite exposed end of at least one of the pair of lead wires in an airproof state between the bead and the at least one of the pair of leadwires.
 7. The filament electrode according to claim 2, wherein the pairof connecting pipes are each formed in a tapered shape so as to shrinkfrom each first end of the pair of connecting pipes towards eachrespective opposite end of the pair of connecting pipes.
 8. The filamentelectrode according to claim 7, wherein the pair of connecting pipesincludes a getter material that functions as a getter.
 9. The filamentelectrode according to claim 8, further comprising: a bead formed in asubstantially circular shape, wherein the bead is located adjacent theopposite exposed end of at least one of the pair of lead wires in an airproof state between the bead and the at least one of the pair of leadwires.
 10. The filament electrode according to claim 7, furthercomprising: a bead formed in a substantially circular shape, wherein thebead is located adjacent the opposite exposed end of at least one of thepair of lead wires in an air proof state between the bead and the atleast one of the pair of lead wires.
 11. The filament electrodeaccording to claim 2, wherein the pair of connecting pipes includes agetter material that functions as a getter.
 12. The filament electrodeaccording to claim 11, further comprising: a bead formed in asubstantially circular shape, wherein the bead is located adjacent theopposite exposed end of at least one of the pair of lead wires in an airproof state between the bead and the at least one of the pair of leadwires.
 13. The filament electrode according to claim 2, furthercomprising: a bead formed in a substantially circular shape, wherein thebead is located adjacent the opposite exposed end of at least one of thepair of lead wires in an air proof state between the bead and the atleast one of the pair of lead wires.
 14. A fluorescent lamp includingthe filament electrode according to claim 13, comprising: a tubeconfigured in a tubular shape, an inner surface of the tube including aphosphor layer, and each end of the tube including a respective filamentelectrode located opposite to each other and fixed between each end ofthe tube, and including a respective bead including a respective pair oflead wires fixed in the respective bead in an air proof state; and afiller gas located in the tube.
 15. The filament electrode according toclaim 1, wherein the pair of connecting pipes includes a squeezing partlocated between each first end of the pair of connecting pipes and eachrespective opposite end of the pair of connecting pipes.
 16. Thefilament electrode according to claim 15, wherein the pair of connectingpipes includes a getter material that functions as a getter.
 17. Thefilament electrode according to claim 16, further comprising: a beadformed in a substantially circular shape, wherein the bead is locatedadjacent the opposite exposed end of at least one of the pair of leadwires in an air proof state between the bead and the at least one of thepair of lead wires.
 18. The filament electrode according to claim 15,further comprising: a bead formed in a substantially circular shape,wherein the bead is located adjacent the opposite exposed end of atleast one of the pair of lead wires in an air proof state between thebead and the at least one of the pair of lead wires.
 19. A fluorescentlamp including the filament electrode according to claim 18, comprising:a tube configured in a tubular shape, an inner surface of the tubeincluding a phosphor layer, and each end of the tube including arespective filament electrode located opposite to each other and fixedbetween each end of the tube, and including a respective bead includinga respective pair of lead wires fixed in the respective bead in an airproof state; and a filler gas located in the tube.
 20. The filamentelectrode according to claim 1, wherein the pair of connecting pipes areeach formed in a tapered shape so as to shrink from each first end ofthe pair of connecting pipes towards each respective opposite end of thepair of connecting pipes.
 21. The filament electrode according to claim20, wherein the pair of connecting pipes includes a getter material thatfunctions as a getter.
 22. The filament electrode according to claim 21,further comprising: a bead formed in a substantially circular shape,wherein the bead is located adjacent the opposite exposed end of atleast one of the pair of lead wires in an air proof state between thebead and the at least one of the pair of lead wires.
 23. The filamentelectrode according to claim 20, further comprising: a bead formed in asubstantially circular shape, wherein the bead is located adjacent theopposite exposed end of at least one of the pair of lead wires in an airproof state between the bead and the at least one of the pair of leadwires.
 24. The filament electrode according to claim 1, wherein the pairof connecting pipes includes a getter material that functions as agetter.
 25. The filament electrode according to claim 24, furthercomprising: a bead formed in a substantially circular shape, wherein thebead is located adjacent the opposite exposed end of at least one of thepair of lead wires in an air proof state between the bead and the atleast one of the pair of lead wires.
 26. A fluorescent lamp includingthe filament electrode according to claim 25, comprising: a tubeconfigured in a tubular shape, an inner surface of the tube including aphosphor layer, and each end of the tube including a respective filamentelectrode located opposite to each other and fixed between each end ofthe tube, and including a respective bead including a respective pair oflead wires fixed in the respective bead in an air proof state; and afiller gas located in the tube.
 27. The filament electrode according toclaim 1, further comprising: a bead formed in a substantially circularshape, wherein the bead is located adjacent the opposite exposed end ofat least one of the pair of lead wires in an air proof state between thebead and the at least one of the pair of lead wires.
 28. A fluorescentlamp including the filament electrode according to claim 27, comprising:a tube configured in a tubular shape, an inner surface of the tubeincluding a phosphor layer, and each end of the tube including arespective filament electrode located opposite to each other and fixedbetween each end of the tube, and including a respective bead includinga respective pair of lead wires fixed in the respective bead in an airproof state; and a filler gas located in the tube.
 29. The fluorescentlamp of claim 28, wherein the tube is a glass tube.
 30. The filamentelectrode according to claim 27, wherein the bead is a glass bead.